Difference between revisions of "Boolean constants"
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In this case the return value of the function (TRUE/FALSE) has the same logic characteristics as the sub-expression (x == y) in the example above. So you can treat the function call as a boolean sub-expression just like (x == y) and therefore the same logic leads to the same conclusion concerning the overall expression. | In this case the return value of the function (TRUE/FALSE) has the same logic characteristics as the sub-expression (x == y) in the example above. So you can treat the function call as a boolean sub-expression just like (x == y) and therefore the same logic leads to the same conclusion concerning the overall expression. | ||
| − | However, testing for FALSE or | + | However, testing for FALSE or NOT TRUE is perfectly acceptable: |
<pre> | <pre> | ||
if( IsObjectValid( oObject) == FALSE) ... <-- this is not redundant | if( IsObjectValid( oObject) == FALSE) ... <-- this is not redundant | ||
Revision as of 23:57, 24 October 2009
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| Constant name | Type | Value | Description | Source |
|---|---|---|---|---|
| FALSE | int | 0 | script.ldf | |
| TRUE | int | 1 | script.ldf |
Remarks
If you test for a variable's truth value by testing if it is equal to TRUE you may not get the correct result, since TRUE == 1 is a true expression but TRUE == 2 is not. You may wish to instead test if your variable is not equal to FALSE.
Note also that it is never necessary, and furthermore wasteful, to explicitly "test for TRUE" or "test for NOT FALSE" in a boolean expression anyway. One would never write, for example:
if( (x == y) == TRUE ) ... <-- redundant comparison with TRUE if( (x == y) != FALSE ) ... <-- redundant comparison with FALSE
because the sub-expression (x == y) will evaluate to TRUE or FALSE already. Additionally comparing the result to TRUE (or NOT FALSE) gives the exact same result for the entire expression as leaving the extraneous comparison out completely does. Thus the comparison with TRUE (or NOT FALSE) is redundant, unnecessary and a wasteful computation.
The same logic applies to expressions involving function calls. If a function returns a TRUE/FALSE value, it would be a redundant waste of CPU cycles to test if the returned value was TRUE.
if( IsObjectValid( oObject) == TRUE) ... <-- this is redundant as well if( IsObjectValid( oObject) ) ... <-- same thing, one less comparison
In this case the return value of the function (TRUE/FALSE) has the same logic characteristics as the sub-expression (x == y) in the example above. So you can treat the function call as a boolean sub-expression just like (x == y) and therefore the same logic leads to the same conclusion concerning the overall expression.
However, testing for FALSE or NOT TRUE is perfectly acceptable:
if( IsObjectValid( oObject) == FALSE) ... <-- this is not redundant if( IsObjectValid( oObject) != TRUE) ... <-- this is not redundant either if( !IsObjectValid( oObject) ) ... <-- but this might be the best method
The identifier TRUE is only really useful for defining default values of boolean type parameters in a function definition, passing a true value to a function with a boolean parameter when you call it, or setting the value of a boolean type variable. There is no other place where you need it.
void Dance( int bChaCha = TRUE)... <-- default value in function def SetItemDroppable( oItem, TRUE); <-- boolean parameter in function call int bStillLooking = TRUE; <-- set a variable value
Some will probably take the position that having the extra comparison in there makes the code more readable and obvious. It would be difficult to argue that point especially in some more complex expression situations. But it is functionally unnecessary and adding it does waste CPU cycles in exchange for that marginal increase in readability. Learning to read experessions without it having to be there would benefit anybody.
